Gable top cartons have been known for the better part of the twentieth century. Their characteristic simplicity and resealability have helped to sustain their popularity as containers for traditional liquid food products such as milk and juice, but in recent years they have been used for products ranging from ammunition to Epsom salts. Gable top cartons typically start out as generally rectangular carton blanks made of laminated paperboard or similar material. The carton blanks are provided with a number of creases to facilitate folding and forming the blank into a carton.
During decades of development, manufacturers of packaging machines have devised a variety of ways to form, fill and seal gable top cartons. Today, the most prevalent packaging machines for gable top cartons are adapted to receive the carton blank after it has been side sealed. The process of side sealing opposite vertical edges of the carton blank together to form a polygonal (usually rectangular) sleeve. The sleeve is received on an indexable mandrel wheel, which rotates the sleeve into respective positions where the end of the sleeve extending outwardly from the mandrel is folded and sealed to form the bottom of the carton.
After the carton bottom has been formed, the carton is then removed from the mandrel and transposed to a filing station, where the carton is filled with product. Once the carton has been filled, the top of the carton is folded and into the familiar gable top configuration and is heat sealed, thus completing the packaging process. One example of a known packaging machine that operates generally in accordance with these principles is described in U.S. Pat. No. 3,789,746 to Martensson et al.
When the top panels of the container are folded to form the familiar gable top configuration, a channel is formed at the mid-section of the top fin. The channel extends from the interior to the exterior of the container and is exposed to the product contents. The channel must therefore be sealed to prevent leakage of the product. Traditionally, the channel of the top fin has been sealed by forming either a vertically or horizontally extending stake at the channel site. During the sealing process, a pair of sealing jaws compress the top fin. The jaws have raised portions that form the stake.
The traditional stake configurations break the barrier material in the region of the channel thereby leaving portions of the paperboard exposed to the product. When the product, for example, is a liquid such as milk or orange juice, the product begins "wicking" through the paperboard substrate of the top fin. Such wicking may compromise the seal of the top fin over the shelf life of the product and, further, may result in an accumulation of the product along the top fin that may be repulsive to the consumer when the carton is opened.